1. Field of the Invention
The present invention generally relates to 3-dimensional scanning and measuring systems and more particularly relates to a system for generating accurate and complete 3-dimensional models from objects using a structured light source operated manually by an operator.
2. Description of the Related Art
Three-dimensional (3D) models of objects can provide information useful for a variety of applications such as generating computer aided design models from physical objects in product designs, outlining biological structures or organs in medical research and simulating natural scenes for training. Nevertheless, the creation of the 3D models has in the past required highly skilled professionals, extensive artistic knowledge, expensive modeling equipment and laborious efforts.
With the popularity of personal computers and the rapid emergence of the Internet and the World Wide Web (www), there are increasing demands from non-professionals for 3D modeling systems that require no extensive knowledge to operate. For example, a business may need to generate 3D models of its products and present them on its www site to attain its e-commence presence. A real estate agent may need to provide prospective buyers with an interactive preview of properties without driving around. A child may want to generate a 3D image of one of his/her favorite new toys to share by the Internet with a relative living remotely. The various applications and demands have proclaimed features of such 3D modeling systems that must be low in cost and easy in operation.
One of the commonly used 3D modeling systems is a triangulation system projecting beams of laser light onto an object. Ordinarily, the reflected light bounces off the object at an angle relative to the light source. The system employing an imaging system collects the reflection information from a different location relative to the light source and then determines the coordinates of the point or points of reflection by triangulation. A single dot system projects a single beam of light which, when reflected, produces a single dot of reflection. A scanning line system sends a plane of light against the object, the plane of light is reflected as a curvilinear-shaped set of points describing one contour line of the object. The location of each point in that curvilinear set of points can be determined by triangulation. The accuracy of the systems may be high but the systems are costly. The triangulation in the systems requires a precise configuration between the light source and the imaging system. Further the digitizing speed is usually slow when the object is large in size and limited by the mechanics of the scanning system.
Another commonly used 3D modeling approach is image based systems employing one or more imaging systems located at known locations or distances from each other to take multiple images of a 3D object. The captured images are processed with a pattern recognition system that corresponds the various points of the object in the multiple images and triangulates to extract depth information of these points, thereby obtaining the shape/contour information of the 3D object. However, it is known that some concave portions of the 3D object""s surface can be unobservable to the imaging systems, which may result in errors in final 3D models.
Recent product introductions, technological advancements, and price cuts have made imaging systems ubiquitous, so it is likely that image based systems will be one of the most popular 3D modeling systems to generate 3D models of objects for many applications. There is therefore a great need for a mechanism that can complement the image based 3D modeling systems to create accurate 3D models with minimum effort.
The present invention has been made in consideration of the above described problems and needs and has particular applications for image-based 3D modeling systems. According to one aspect of the present invention, a commercially available structured light projector such as a laser pointer projecting a stripe is employed and swung manually across a particular area of interest on the surface of an object. The particular area of interest includes typically those hidden curvatures that are unobservable or otherwise difficult to be imaged by a camera-based imager. Under the illumination of the swinging laser stripe, the object is successively imaged to produce a sequence of images. From each of the images, a set of curvilinear points from the (deformed) projected line falling on the area of interest are calculated in conjunction with a calibration model of the imager. As used herein, a set of curvilinear points mean a group of successive points or pixels representing surface curvatures of a 3D object, graphic illustrations thereof are provided wherever appropriate. The curvilinear points from all the images are then merged to provide accurate and complete 3D data about the area of interest. The 3D data can be incorporated to correct, modify or otherwise enrich a 3D model derived from an image-based modeling system. As such a precise 3D model of the object can be generated with minimum effort.
According to another aspect of the present invention, the laser pointer is swung manually across a 3D object while several or surrounding views of the object are imaged by an imager, in which either the imager is moved around the object or the object is rotated. According to the same principles, for each of the views, sets of curvilinear points describing contours of the object are calculated. All the curvilinear points from all the views are then xe2x80x9cstitchedxe2x80x9d together to derive a 3D model of the object.
According to still another aspect of the present invention, a pair of flat panels are used to provide a reference for dynamically determining the position of a manually operated light source projecting a light stripe onto a 3D object. The flat panels, such as a turntable and a background reference, are configured to a known angle, preferably 90xc2x0 to form a bifurcated or angled background. An object to be modeled is placed on a horizontal plane and in front of a vertical plane or simply in front of the two angled planes. When the object is illuminated by the light stripe being swung repeatedly (e.g. back and forth or up and down), the scene is imaged by a pre-calibrated imager to produce a sequence of images. Each of the images includes two non-deformed reflected light segments reflecting the projected light stripe falling respectively on the two flat panels. By detecting the two light segments in each of the images, the position and orientation of a light sheet intersecting the two light segments are derived so as to determine the position and orientation of the stripe from the light source. Thus a dynamic calibration of the light source is achieved.
The invention can be implemented in numerous ways, including a method, system, computer readable medium containing program code for generating a 3D model of an object using a structured light source projecting a plane of light or stripe. Each has achieved unexpected results and benefits.
The advantages of the invention are numerous. Different embodiments or implementations may yield one or more of the following advantages. One of them is an economical and efficient supplemental mechanism that can be employed to obtain accurate, complete, and timely as-built geometry information of a particular area of an object or a large structure. Another one is an extremely high level of detail of the particular area of the interest the present invention can provide. For those narrow or deep concavities, the user can swing the laser from a position closer to the imager to increase the coverage of the narrow/deep concavities. Still another one is the reduction to practice of an extremely low-cost 3D modeling system using a structured light source operated manually. Conventional 3D modeling systems using structured light sources require precise configuration between the light sources and an imaging device. In contrast, the present invention provides an approach to dynamically calibrate/determine the position of the light source projecting a light stripe by initially detecting the light stripe falling on two flat panels that form an angled background, thereby requiring no fixed configuration between the light source and the imaging device. As a result, a user is now allowed to swing the light stripe from any position with respect to the imager to illuminate any particular area of the interest of an object or objects of any sizes to derive 3D models thereof. In addition, the dynamic calibration may be performed using a portion of wall/floor or two walls of any room, or the wall/ground of any building exterior. Thus large objects such as furniture and automobiles may be scanned and modeled electronically.
Other advantages, benefits, objects and features of the present invention, together with the foregoing, are attained in the exercise of the invention in the following description and resulting in the embodiment illustrated in the accompanying drawings.